Question

Assertion; The plasma membrane is trilaminar
Reason;One optically light layer is lipids and on both sides of it two optically denser layers of proteins are present.
A)Both assertion and reason are correct and the reason is the correct explanation for assertion
B)Both Assertion and Reason are correct but the reason is not the correct explanation for assertion
C)Assertion is correct but Reason is incorrect
D)Both assertion and reason are incorrect

Answer 1

Hint: Every cell is surrounded by a transparent electron microscopic, regenerative, and selectively permeable membrane known as the plasma membrane. It is semi-fluid in nature and occurs inside the cell. They are generally called biomembranes. The name Plasma membrane was replaced by the term plasmalemma by Plower (1931).

Complete answer:
-The unit membrane concept for the model of the plasma membrane proposed by Robertson in the year 1960.
-The unit membrane comprises a bimolecular lipid as a sandwich present between the outer and the inner layer of proteins which is organized in the pleated sheet configuration. Therefore, according to Robertson, the plasma membrane is a trilaminar structure.
-An optically dense layer of proteins surrounded the lipid bilayer from the outer and inner side of the plasma membrane.

Additional Information: -Lipids and proteins are the major component of the plasma membrane forming 60% of it.
-The mechanical strength provided by the proteins which are responsible for the transportation of different substances. It also acts as an enzyme.
-Depending on the type of cell and the organisms involved lipids account for 28 to 79% of the plasma membrane.
-Phospholipids, glycolipids, and sterols are the three types of lipids present in the plasma membrane.
-The carbohydrate which is present in the plasma membrane is the oligosaccharide. It forms 2 to 10% of the Plasma membrane. They are covalently linked to protein and lipid components.
Functions of the plasma membrane
1)It provides mechanical strength and also acts as a protective layer.
2)It is possible for the transportation of materials, molecules, ions, etc.
3) It also helps in the osmoregulation.
4)Through the plasma membrane, the diffusion of gases takes place by simple and facilitated diffusion.
5)Through its membrane pores, some solute molecules and ions pass
So, the correct answer is, "Both assertion and reason are correct and the reason is the correct explanation for assertion".

Note: -According to the Robertson model, the protein layer formed from a monolayer of peptides chains rather than whole protein molecules.
-The long-chain molecules from which the proteins are made known as polypeptides.
-On the exterior of the membrane, the polypeptide layer is present.